Overweight and obesity

Most people know what the term obesity means: an increased body weight caused by the excessive accumulation of fat. Overweight and obesity occur when more calories are taken into the body than are burnt up over time. In other words, if you don’t burn up the energy you consume it will be stored as fat, and over time this may lead to excessive weight gain and obesity. So someone who works in a very physically demanding job, such as a building-site labourer, may need between 4,000 and 5,000 calories per day to maintain their normal weight. Whereas an office worker, who drives to work and does not take any exercise, may only need 1,500 calories per day.

Another way of defining obesity is to measure your body mass index (BMI). This is your weight in kilograms divided by the square of your height in metres. There are many websites that can do conversions and calculations for you (see Appendix II). In England, people with a body mass index between 25 and 29 are categorised as overweight, and those with an index of 30 or above are categorised as obese. If your BMI is over 40, you would be described as morbidly obese. The UK government describes 18.5 to 25 as healthy and suggests that a BMI of less than 18.5 is underweight. Alternatively, another useful method is to measure around your waist. People with very fat waists (94cm or more in men and 80cm or more in women) are more likely to develop obesity-related health problems.

Abdominal fat (also known as internal or visceral fat) is of particular concern because it’s a key player in a variety of health problems including high blood pressure and cholesterol (which can lead to heart disease), diabetes and some cancers. You don’t have to be overweight or obese to have high levels of this type of fat. Some slim people, who do little or no exercise, can have elevated levels of visceral fat. Unlike subcutaneous fat (the kind you can grasp with your hand), visceral fat lies deep within the abdominal region, hidden in the white fat that surrounds the vital organs, streaked through underused muscles and wrapped around the heart. An MRI scan will reveal how much visceral fat a person has but from the outside it is impossible to tell. Hence the term ‘tofi’ – thin on the outside, fat on the inside. Such people are less likely to think they need to change their lifestyle and could unwittingly be at risk of serious health consequences. Research suggests that diet and exercise can be very effective in helping reduce visceral fat. Complex carbohydrates (fruits, vegetables and whole grains) and limiting the intake of simple carbohydrates such as white bread, white pasta and sugary drinks can help. Replacing saturated fats with polyunsaturated fats can also help.

In 2008, over a third (35 per cent) of all adults in the world were overweight, and more than one in ten (11 per cent) was obese. From 1980-2008, the worldwide prevalence of obesity nearly doubled with an estimated half a billion adults worldwide being described as obese. The highest levels of overweight and obesity occur in Canada, North and South America with 62 per cent overweight and 26 per cent obese. The lowest figures are seen in South East Asia (14 per cent overweight three per cent obese). In Europe, the Eastern Mediterranean and the Americas, over 50 per cent of women are overweight. For all three of these regions, roughly half of overweight women are obese.

The main causes of obesity include an excessive intake of food coupled to a lack of exercise and a sedentary lifestyle. Other much less frequent causes include a genetic predisposition or an underlying illness (such as hypothyroidism). The British Medical Association (BMA) warns that childhood obesity levels have soared in the UK over recent years. They say that just over a quarter of adults in England are obese and three out of 10 children aged 2-15 in England are overweight or obese. They warn that by 2050, it is estimated that half of the population in England will be obese.

The BMA attribute this rise to the fact that children are eating too much for the amount of physical activity they undertake. This is very worrying as early childhood obesity tends to indicate adult obesity which can lead to serious health risks later in life. Obesity is a known risk factor for many illnesses including type 2 diabetes, heart disease, high blood pressure, stroke, gall bladder disease and certain forms of cancer especially the hormonally related and large-bowel cancers. Childhood obesity is associated with a higher chance of obesity, premature death and disability in adulthood. But in addition to increased future risks, obese children experience breathing difficulties, increased risk of fractures, high blood pressure, early markers of CVD, insulin resistance and psychological effects.

As populations become more urban and incomes rise, diets high in sugar, fat and animal products replace more traditional diets that were high in complex carbohydrates and fibre. Ethnic cuisine and unique traditional food habits are being replaced by westernised fast foods, soft drinks and increased meat consumption. Homogenisation and westernisation of the global diet has increased the energy density and this is particularly a problem for the poor in all countries who are at risk of both obesity and micronutrient deficiencies. This combined with a shift towards less physically demanding work, an increasing use of automated transport, technology in the home and more passive leisure pursuits means that people are less active than their parents and grandparents.

The WHO suggests several ways to lose weight including eating more fruit, vegetables, nuts and whole grains; engaging in daily moderate physical activity (60 minutes a day for children and 150 minutes per week for adults); cutting the amount of fatty, sugary foods in the diet and moving from saturated animal-based fats to unsaturated vegetable-oil based fats. Whole milk, cheese, cream, butter, ice-cream and most other dairy products, apart from skimmed and non-fat products, contain significant amounts of saturated fat and cholesterol. While we do need a certain amount of fat in the diet there is no nutritional requirement for saturated fat. Cow’s milk is high in the unhealthy saturated fats and low in the healthy polyunsaturated essential fatty acids, which are required in the diet for good health. Most people eat much more fat than they need, and making minor changes to the diet (cutting down on fat) can make a big difference over time.

The Department of Health recommends that saturated fat should contribute no more than 11 per cent of the total energy that we get from food (Department of Health, 1991). Most people consume more than that. The 2012 National Diet and Nutrition Survey found that on average, saturated fat made up 12.8-13.6 per cent of food energy in all groups aged between four and 64. Compared with previous surveys, saturated fat intakes were somewhat lower in this study but, for adults, no statistically significant changes were observed. In general, the differences in absolute intake of saturated fat were relatively small (1-3g per day). Clearly we are failing to heed the advice to reduce our intake of saturated fat.

Milk and dairy foods make a significant impact on saturated fat in the diet. Most saturated fat in the average UK diet comes from: milk, cheese, ice-cream, butter, margarine and fat-based spreads along with meat, pastry products (pies, tarts etc), bakery products (buns, biscuits, cakes), chocolate and chocolate confectionery and snacks. Approximately 65 per cent of the fat in milk is saturated and about three per cent of food energy is from dairy products making this a major target.

A number of small-scale studies (of less than 35 obese adults) have suggested that the consumption of dairy products may actually help people lose weight. In these studies Professor Zemel, who has received a considerable amount of funding from the National Dairy Council, suggested that diets containing calcium from dairy foods might affect fat cell metabolism in such a way that greater weight loss can occur despite an identical calorie intake with a control group not consuming so much dairy.

The US National Dairy Council (who funded Zemel’s research) is overseen by Dairy Management Incorporated, a non-profit corporation that defines its mission as increasing sales and demand for dairy products. Not dissimilar to the UK’s dairy industry-funded DairyCo, Dairy Management Incorporated is funded by America’s dairy farmers via a government-mandated fee. In 2009 they also received $5.3 million from the Agriculture Department to promote dairy sales overseas. In 2010, Dairy Management’s annual budget approached a staggering $140 million. By comparison, the Center for Nutrition Policy and Promotion, which promotes healthy diets, had a total budget of just $6.5 million.

Dairy Management Incorporated has relentlessly marketed cheese despite the fact that Agriculture Department data show that cheese is a major reason the average US diet contains too much saturated fat. They employed a whole new marketing strategy with a weight-loss campaign based on Zemel’s research. However, a subsequent study (by a research group including Zemel but not as the first named author) found no evidence that a diet high in dairy products enhances weight loss. Furthermore, research that they also hoped would support Zemel’s work found no evidence of dairy-related weight loss. Dairy Management Incorporated pressed on with its advertising campaign regardless.

Dr Amy Lanou, the nutrition director of the PCRM, warned that care should be taken when interpreting the findings from Zemel’s trials. Furthermore, Lanou suggested that the US National Dairy Council’s claims promoting dairy consumption for weight loss went well beyond Zemel’s findings. Lanou suggests that it was likely that calorie restriction, not dairy consumption, caused the weight loss reported in these studies.

In June 2005 the PCRM decided enough was enough and filed two separate lawsuits to stop the multimillion-dollar advertising campaign claiming that milk facilitates weight loss. They filed one lawsuit to the US Food and Drugs Administration and the other to the US Federal Trade Commission. In the lawsuit the PCRM charged the National Dairy Council, the International Dairy Foods Association, Dairy Management Incorporated, Dannon Company, Kraft Foods and other dairy manufacturers with purposefully misleading customers. Astonishingly, government lawyers defended the campaign, saying that the Agriculture Department reviewed, approved and continually oversaw the effort. Dr Walter C. Willett, chairman of the nutrition department at the Harvard School of Public Health and a former member of the federal government’s nutrition advisory committee, said: “The USDA should not be involved in these programs that are promoting foods that we are consuming too much of already. A small amount of good-flavoured cheese can be compatible with a healthy diet, but consumption in the U.S. is enormous and way beyond what is optimally healthy”.

The dairy industry’s national advertising campaign promoting the notion that people could lose weight by consuming more dairy products went on for a total of four years finally ending in 2007 when the Federal Trade Commission acted on the two-year-old petition by the PCRM. The Agriculture Department and dairy officials agreed to halt the campaign pending further research. Dairy Management Incorporated moved on to promoting milk and dairy foods in other areas such as promoting chocolate milk in schools and encouraging companies like Domino’s pizza to use even more cheese in its pizzas (Domino’s Wisconsin pizza now has six cheeses on top and two more in the crust). In an article in the New York Times, Dr Neal D. Barnard, president of the PCRM said: “If you want to look at why people are fat today, it’s pretty hard to identify a contributor more significant than this meteoric rise in cheese consumption”. This may seem little to do with overweight and obesity problems in the UK, but these issues are mirrored here and trends show that we are not that far behind the extreme levels of obesity seen in the US.

Despite the dairy industry’s claims outlined above, scientific studies show that adding dairy products to the diet does not help control weight; in fact the research confirms that in many cases the reverse is true, consuming milk and dairy foods can lead to weight gain. Some studies designed to test the effects of dairy consumption on weight found no difference in weight between groups consuming relatively large amounts of dairy foods compared to groups consuming little. Another study, this time of the effects of just calcium supplementation on weight loss in women who had recently given birth, found no relationship between calcium supplementation and weight loss. Researchers at the University of British Columbia in Vancouver, Canada, who reviewed the scientific literature on the effects of dairy products or calcium supplements on body weight found that out of nine studies on dairy products, seven showed no significant difference while two studies linked weight gain to dairy consumption. Furthermore, out of 17 studies on calcium supplementation, just one reported weight loss. The authors state that interpreting such findings is limited by the inability to accurately determine the extent of compensation for the energy intake from the added dairy products. In other words, people who increased their dairy intake may have maintained the same energy intake (and so not gained weight) by reducing other foods. For example, the authors of one of the studies reviewed noted that the dairy product group in their study may have reduced their consumption of baked goods to compensate for the additional intake of dairy foods. Furthermore serious questions have arisen regarding the ability of diet records to reflect actual energy intake.

Another large scale study that followed over 12,000 children for three years concluded that the children who drank the most milk gained the most weight. The analyses showed that out of milk, calcium, dairy fat and total energy intake, it was energy intake that was the most important predictor of weight gain. The authors attribute this weight to… you’ve guessed it, the added calories!

On the other hand, numerous studies show that a low-fat plant-based diet can be very effective in helping lose and maintain a healthy weight. A recent study looked at the effects of eating a low-fat plant-based diet for 18 weeks on body weight and CVD risk in people with a BMI of 25 or higher and/or a previous diagnosis of type 2 diabetes. Results showed the average weight loss was 2.9 kg (compared to 0.06 kg in the control group). Total and LDL (‘bad’) cholesterol also fell in the test group. It was concluded that dietary intervention using a low-fat plant-based diet improves body weight, plasma lipids and in individuals with diabetes, it can also help control blood sugar levels.

To most people it is just common sense, a calorie is a calorie and weight gain or weight loss is a case of mathematics. If you take in more energy (calories) than you use, you will gain weight. If you use up more energy than you consume, you will lose weight. There is no magic bullet, and if there were it seems very unlikely that it would be cow’s milk, butter or cheese.